Mobile terminal and base station involved in downlink channel operations including radio channel estimation based on demodulation reference signal

ABSTRACT

The present disclosure relates to a mobile terminal, a base station and respective operation methods. The mobile terminal comprises circuitry, which in operation assumes that a base station is configured to use one of a plurality of transmission beams, receives a downlink control channel candidate and a corresponding demodulation reference signal using one of a plurality of reception beams corresponding to the assumed one of the plurality of transmission beams, performs channel estimation based on the received demodulation reference signal, and, depending on the quality, demodulates the downlink control channel candidate using the channel estimation. The channel estimation is performed using a demodulation reference signal sequence which is generated observing an association which is associating the generated sequence with the assumed one of the plurality of transmission beams such that at least two of the plurality of transmission beams are associated with different demodulation reference signal sequences.

BACKGROUND Technical Field

The present disclosure is directed to methods, devices and articles incommunication systems, such as 3GPP communication systems.

Description of the Related Art

Currently, the 3rd Generation Partnership Project (3GPP) works at thetechnical specifications for the next generation cellular technology,which is also called fifth generation (5G).

One objective is to provide a single technical framework addressing allusage scenarios, requirements and deployment scenarios (see e.g.,section 6 of TR 38.913 version 15.0.0 incorporated herein by reference),at least including enhanced mobile broadband (eMBB), ultra-reliablelow-latency communications (URLLC), massive machine type communication(mMTC).

For example, eMBB deployment scenarios may include indoor hotspot, denseurban, rural, urban macro and high speed; URLLC deployment scenarios mayinclude industrial control systems, mobile health care (remotemonitoring, diagnosis and treatment), real time control of vehicles,wide area monitoring and control systems for smart grids; mMTCdeployment scenarios may include scenarios with large number of deviceswith non-time critical data transfers such as smart wearables and sensornetworks.

The services eMBB and URLLC are similar in that they both demand a verybroad bandwidth, however are different in that the URLLC service maypreferably require ultra-low latencies.

A second objective is to achieve forward compatibility. Backwardcompatibility to Long Term Evolution (LTE, LTE-A) cellular systems isnot required, which facilitates a completely new system design and/orthe introduction of novel features.

BRIEF SUMMARY

One non-limiting and exemplary embodiment facilitates providing animproved procedure for the mobile terminal to perform downlink controlchannel receptions and an improved procedure for the base station toperform downlink control channel transmissions.

In one general first example, the techniques disclosed here feature auser equipment comprising a processing circuitry and transceiver. Theprocessing circuitry assumes that a base station is configured to usefor downlink control channel (PDCCH) and corresponding demodulationreference signal (DM-RS) transmissions to the mobile terminal one of aplurality of transmission beams (tx-beam #1). The transceiver receives adownlink control channel candidate (PDCCH candidate) and a correspondingdemodulation reference signal (DM-RS) from the base station using one ofa plurality of reception beams (rx-beam #1) corresponding to the assumedone of the plurality of transmission beams (tx-beam #1). The processingcircuitry (130) performs radio channel estimation based on the receiveddemodulation reference signal (DM-RS). The processing circuitry,depending on a radio channel estimation quality, demodulates thedownlink control channel candidate (PDCCH candidate) using the radiochannel estimation. The channel estimation is performed using ademodulation reference signal sequence which is generated observing anassociation which is associating the generated sequence with the assumedone of the plurality of transmission beams (tx-beam #1) such that atleast two of the plurality of transmission beams are associated withdifferent demodulation reference signal sequences.

In one general first example, the techniques disclosed here feature abase station comprising processing circuitry and a transceiver. Theprocessing circuitry (180) assumes that the mobile terminal isconfigured to use for downlink control channel (PDCCH) and correspondingdemodulation reference signal (DM-RS) receptions at the mobile terminalone of a plurality of reception beams (tx-beam #1). The transceiver(170) transmits a downlink control channel (PDCCH) and correspondingdemodulation reference signal (DM-RS) to the mobile terminal using oneof a plurality of transmission beams (tx-beam #1) corresponding to theassumed one of the plurality of reception beams (tx-beam #1). Theprocessing circuitry (180) modulates the downlink control channel(PDCCH) to be transmitted and generates a demodulation reference signalsequence to be transmitted as the corresponding demodulation referencesignal (DMRS). The demodulation reference signal sequence is generatedobserving an association which is associating the generated sequencewith the one of the plurality of transmission beams (tx-beam #1) suchthat at least two of the plurality of transmission beams are associatedwith different demodulation reference signal sequences.

In one general first example, the techniques disclosed here feature amethod comprising the following steps performed by a user equipment. Themobile terminal assumes that a base station is configured to use fordownlink control channel (PDCCH) and corresponding demodulationreference signal (DM-RS) transmissions to the mobile terminal one of aplurality of transmission beams (tx-beam #1). The mobile terminalreceives a downlink control channel candidate (PDCCH candidate) and acorresponding demodulation reference signal (DM-RS) from the basestation using one of a plurality of reception beams (rx-beam #1)corresponding to the assumed one of the plurality of transmission beams(tx-beam #1). The mobile terminal performs radio channel estimationbased on the received demodulation reference signal (DM-RS) and,depending on a radio channel estimation quality, demodulates thedownlink control channel candidate (PDCCH candidate) using the radiochannel estimation. The channel estimation is performed using ademodulation reference signal sequence which is generated observing anassociation which is associating the generated sequence with the assumedone of the plurality of transmission beams (tx-beam #1) such that atleast two of the plurality of transmission beams are associated withdifferent demodulation reference signal sequences.

In one general first example, the techniques disclosed here feature amethod comprising the following steps performed by a base station. Thebase station assumes that the mobile terminal is configured to use fordownlink control channel (PDCCH) and corresponding demodulationreference signal (DM-RS) receptions at the mobile terminal one of aplurality of reception beams (tx-beam #1). The base station transmits adownlink control channel (PDCCH) and corresponding demodulationreference signal (DM-RS) to the mobile terminal using one of a pluralityof transmission beams (tx-beam #1) corresponding to the assumed one ofthe plurality of reception beams (tx-beam #1). The base stationmodulates the downlink control channel (PDCCH) to be transmitted andgenerates a demodulation reference signal sequence to be transmitted asthe corresponding demodulation reference signal (DMRS). The demodulationreference signal sequence is generated observing an association which isassociating the generated sequence with the one of the plurality oftransmission beams (tx-beam #1) such that at least two of the pluralityof transmission beams are associated with different demodulationreference signal sequences.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments anddifferent implementations will be apparent from the specification andfigures. The benefits and/or advantages may be individually obtained bythe various embodiments and features of the specification and drawings,which need not all be provided in order to obtain one or more of suchbenefits and/or advantages.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following exemplary embodiments are described in more detail withreference to the attached figures and drawings.

FIG. 1 illustrates the exemplary and simplified structure of a mobileterminal and a base station,

FIG. 2 depicts a structure of the mobile terminal and the base stationaccording to an exemplary implementation;

FIG. 3 shows an exemplary implementation of an association betweentransmit beams and demodulation reference signal generating basesequences

FIG. 4 details an another exemplary implementation of an associationbetween transmit beams and demodulation reference signal generating basesequences,

FIGS. 5a-5c display an exemplary mechanism for creating demodulationreference signal generating base sequences,

FIGS. 6 and 7 illustrate a flow diagram and a timing diagram of downlinkcontrol channel receptions according to a first exemplary embodiment,

FIGS. 8 and 9 depict a flow diagram and a timing diagram of downlinkcontrol channel receptions according to a second exemplary embodiment,

FIGS. 10-12 show a flow diagram and a timing diagram of downlink controlchannel receptions according to a third exemplary embodiment, and

FIGS. 13 and 14 depict a flow diagram and a timing diagram of the mobileterminal and the base station according to another exemplaryimplementation.

DETAILED DESCRIPTION

In 3GPP NR, the operation in unlicensed spectrum (termed NR-U) hasgreatly improved over mechanisms known from the former versions of, forexample, the LTE standards. In its efforts to standardize thisoperation, 3GPP has devoted a study item, i.e., 3GPP RP-172021 to thistopic, which in its entirety is incorporated herein by reference. Forexample, in section 4.1 of this document, the different architecturalscenarios are discussed, including NR-based Licensed Assisted Access(LAA), and an NR-based standalone cell operation in unlicensed spectrum.

Overview

As defined in Release-15, all Release-15 NR UEs in licensed bandoperation will be able to support 100 MHz bandwidth for sub-6 GHz (e.g.,bands in 450 MHz-6 GHz)), and 400 MHz bandwidth for millimeter wave(e.g., bands in 24.25 GHz-52.6 GHz). In addition, there are several wideunlicensed frequency bands available, which can be made use of in orderto satisfy the everlasting demand for faster, more responsive mobilebroadband. Hence, wideband operation in unlicensed spectrum is one ofthe key building blocks for NR-U.

Another key feature for fourth generation (4G) LTE and 5G New Radio (NR)is multiple-input multiple-output (MIMO) transmission. With the adventof active antenna (AA) arrays, utilizing a large number of antennaelements at base stations (BSs) has become feasible. Moreover,rectangular (2D) AA arrays can be utilized where beamforming can beperformed along each available spatial dimension (e.g., azimuth andelevation).

In the most recent LTE Release (termed full-dimensional MIMO orFD-MIMO), rank-adapted spatial multiplexing with up to 32 digitallyprecoded antenna ports is supported. LTE FD-MIMO is designed to operatein lower frequency bands, known as the sub-6 GHz regime. On the otherhand, as the availability of sub-6 GHz spectrum becomes more limited,millimeter-wave (mmWave) frequency bands (also termed the over-6 GHzregime) with wider bandwidths will be made available for cellularcommunications in 5G. Although promising, its characteristics differfrom sub-6 GHz. For instance, with higher propagation loss, beamformingwith larger number of antenna elements becomes crucial for ensuringsufficient coverage. However, utilizing a large number of digitallyprecoded ports is infeasible in the current device technology. Thisnecessitates so-called hybrid beamforming wherein analog beams are usedwith a small number of digitally precoded ports. Here, user equipment(UE) needs to acquire a set of analog beams in conjunction withMIMO-related digital operations.

As analog antenna processing will be carried out on a carrier basis,this also implies that beam-formed transmission can only be done on onedirection at a time. Downlink transmissions to different devices locatedin different directions relative to the base station must therefore beseparated in time. Likewise, in the case of analog-based receiver-sidebeam-forming, the receive beam can only focus in one direction at time.

Therefore, beam management is required in the 5G NR design. The ultimatetask of beam management is, under these conditions, to establish andretain a suitable beam pair, that is, a transmitter-side beam directionand a corresponding receiver-side beam direction that jointly providegood connectivity.

Operation in Unlicensed Spectrum

As already considered in 3GPP RP-141646, some regions in the worldrequire unlicensed technologies to abide to certain regulations, e.g.,Listen-Before-Talk (LBT). Fair coexistence between cellular operationsand other technologies such as Wi-Fi, in its different versions, as wellas between cellular operators themselves, is necessary.

Even in countries without LBT, regulatory requirements exist to attemptto minimize interference with other users of the unlicensed spectrum.However, it is not enough to minimize interference simply for regulatoryaspects. It is thus, essential to ensure that a NR-based unlicensedaccess wideband system operates as a “good neighbor” towards all formsof legacy systems.

The Listen-Before-Talk (LBT) procedure is defined as a mechanism bywhich an equipment applies a clear channel assessment (CCA) check beforeusing the channel. The CCA utilizes at least energy detection todetermine the presence or absence of other signals on a channel in orderto determine if a channel is occupied or clear, respectively. Europeanand Japanese regulations, for instance, mandate the usage of LBT in theunlicensed bands. Apart from regulatory requirements, this carriersensing via LBT is one way for fair sharing of the unlicensed spectrum,and hence it is considered to be a vital feature for fair and friendlyoperation in the unlicensed spectrum in a single global solutionframework.

Following this European regulation regarding LBT, devices have toperform a Clear Channel Assessment (CCA) before occupying the radiochannel with a data transmission. It is only allowed to initiate atransmission on the unlicensed channel after detecting the channel asfree based e.g., on energy detection. In particular, the equipment hasto observe the channel for a certain minimum time (e.g., for Europe 20μs, see ETSI 301 893, under clause 4.8.3) during the CCA.

The channel is considered occupied if the detected energy level exceedsa configured CCA threshold (e.g., for Europe, −73 dBm/MHz, see ETSI 301893, under clause 4.8.3), and conversely is considered to be free if thedetected power level is below the configured CCA threshold. If thechannel is determined as being occupied, it shall not transmit on thatchannel during the next Fixed Frame Period. If the channel is classifiedas free, the device is allowed to transmit immediately. The maximumtransmit duration is restricted in order to facilitate fair resourcesharing with other devices operating on the same band.

In particular, maximum transmit duration during which an equipment istransmitting on a given carrier without re-evaluating the availabilityof that carrier (i.e., LBT/CCA) is defined as the channel occupancy time(see e.g., ETSI 301 893, clause 4.8.3.1). The channel occupancy timeshall be in the range of 1 ms to 10 ms, where the maximum channeloccupancy time could be e.g., 4 ms as currently defined for Europe.

Present Disclosure

Considering the above, the present disclosure has been conceived by theinventors with the understanding that downlink control channelreceptions require a mobile terminal to perform a non-negligible numberof blind decoding attempts on different downlink control channelcandidates. This blind decoding mechanism results in a non-negligibleprocessing load at the mobile terminal.

Especially when operating in unlicensed spectrum, a mobile terminal mayperform downlink control channel receptions irrespective of whether thechannel has actually been acquired for cellular operation. In otherwords, the mobile terminal will monitor the downlink control channelirrespective of whether the base station has successfully completed theListen-Before-Talk procedure or has failed therewith.

Independent of the timing constraints imposed by Listen-Before-Talk, theprocessing load which is resulting from blind decoding attempts of thedownlink control channel are equally high during unlicensed and licensedoperation.

It is important to understand that the presently available mechanism fordownlink control channel receptions cannot ensure that the processingload is in a fair relationship to successful receptions of downlinkcontrol information carried thereon. Rather, the timing constraintsimposed by Listen-Before-Talk have further worsened this relationship.

The monitoring requirement originates from the specification of searchspace sets in NR (see technical specification 3GPP TS 38.213 versionV15.2.0, published 2018-06 on the website 3gpp.org, and titled, “NR;Physical layer procedures for control (Release 15),” which in itsentirety is incorporated herein by reference; particularly section 10titled “UE procedures for receiving control information” and section11.1 UE procedure for determining “slot format” thereof).

A UE, for example, monitors a set of PDCCH candidates in one or morecontrol resource sets (CORESETs) on the active DL bandwidth-part (BWP)on each activated serving cell configured with PDCCH monitoringaccording to corresponding search space sets where monitoring impliesdecoding each PDCCH candidate according to the monitored DCI formats.

The control resource set is e.g., defined as follows (see section 10.1titled, “UE procedure for determining physical downlink control channelassignment” of 3GPP TS 38.213 referenced above): For each DL BWPconfigured to a UE in a serving cell, a UE can be provided by higherlayer signaling with control resource sets (CORESETs). For each controlresource set (CORESET), the UE is provided the following by higher layerparameter ControlResourceSet:

-   -   a control resource set index p, 0≤p<12, by higher layer        parameter controlResourceSetId;    -   a DM-RS scrambling sequence initialization value by higher layer        parameter pdcch-DMRS-ScramblingID;    -   a precoder granularity for a number of REGs in the frequency        domain where the UE can assume use of a same DM-RS precoder by        higher layer parameter precoderGranularity;    -   a number of consecutive symbols provided by higher layer        parameter duration;    -   a set of resource blocks provided by higher layer parameter        frequencyDomainResources;    -   CCE-to-REG mapping parameters provided by higher layer parameter        cce-REG-MappingType;    -   an antenna port quasi co-location, from a set of antenna port        quasi co-locations provided by higher layer parameter        TCI-StatesPDCCH, indicating quasi co-location information of the        DM-RS antenna port for PDCCH reception;    -   an indication for a presence or absence of a transmission        configuration indication (TCI) field for DCI format 1_1        transmitted by a PDCCH in control resource set p, by higher        layer parameter TCI-PresentInDCI.

For sake of completeness, reference is made to technical specification3GPP TS 38.331 in version V15.2.1 published 2018-06 on the website3gpp.org, and titled, “NR; Radio Resource Control (RRC) protocolspecification (Release 15),” which in its entirety is incorporatedherein by reference. Particular reference is made to section 6.3.2titled, “Radio resource control information element,” thereof, whichdefines the control Resource Set (CORESET) information element, termed“ControlResourceSet IE.”

Additionally, the monitoring of PDCCH candidates is defined to beaccording to corresponding search space sets. A search space set can bea common search space set or a UE-specific search space set. A UEmonitors PDCCH candidates in one or more of the following search spacessets

-   -   a Type0-PDCCH common search space set configured by        searchSpaceZero in MasterInformationBlock or by searchSpaceSIB1        in PDCCH-ConfigCommon for a DCI format with CRC scrambled by a        SI-RNTI on a primary cell;    -   a Type0A-PDCCH common search space set configured by        searchSpace-OSI in PDCCH-ConfigCommon for a DCI format with CRC        scrambled by a SI-RNTI on a primary cell;    -   a Type1-PDCCH common search space set configured by        ra-SearchSpace in PDCCH-ConfigCommon for a DCI format with CRC        scrambled by a RA-RNTI, or a TC-RNTI on a primary cell;    -   a Type2-PDCCH common search space set configured by        pagingSearchSpace in PDCCH-ConfigCommon for a DCI format with        CRC scrambled by a P-RNTI on a primary cell;    -   a Type3-PDCCH common search space set configured by SearchSpace        in PDCCH-Config with searchSpaceType=common for DCI formats with        CRC scrambled by INT-RNTI, or SFI-RNTI, or TPC-PUSCH-RNTI, or        TPC-PUCCH-RNTI, or TPC-SRS-RNTI and, only for the primary cell,        C-RNTI, or CS-RNTI(s); and    -   a UE-specific search space set configured by SearchSpace in        PDCCH-Config with searchSpaceType=ue-Specific for DCI formats        with CRC scrambled by C-RNTI, or CS-RNTI(s).

The following mechanism for configuring search space sets in the UE canbe used (see e.g., section 10.1 titled, “UE procedure for determiningphysical downlink control channel assignment” of 3GPP TS 38.213referenced above).

For each DL BWP configured to a UE in a serving cell, the UE is providedby higher layers with S≤10 search space sets where, for each searchspace set from the S search space sets, the UE is provided the followingby higher layer parameter SearchSpace:

-   -   a search space set index s, 0≤s<40, by higher layer parameter        searchSpaceId;    -   an association between the search space set s and a control        resource set p by higher layer parameter controlResourceSetId;    -   a PDCCH monitoring periodicity of k_(p,s) slots and a PDCCH        monitoring offset of o_(p,s) slots, by higher layer parameter        monitoringSlotPeriodicityAndOffset;    -   a PDCCH monitoring pattern within a slot, indicating first        symbol(s) of the control resource set within a slot for PDCCH        monitoring, by higher layer parameter        monitoringSymbolsWithinSlot;    -   a number of PDCCH candidates M_(p,s) ^((L)) per CCE aggregation        level L by higher layer parameters aggregationLevel1,        aggregationLevel2, aggregationLevel4, aggregationLevel8, and        aggregationLevel16, for CCE aggregation level 1, CCE aggregation        level 2, CCE aggregation level 4, CCE aggregation level 8, and        CCE aggregation level 16, respectively;    -   an indication that search space set S is either a common search        space set or a UE-specific search space set by higher layer        parameter searchSpaceType;    -   if search space set S is a common search space set,        -   an indication by higher layer parameter            dci-Format0-0-AndFormat1-0 to monitor PDCCH candidates for            DCI format 0_0 and DCI format 1_0 with CRC scrambled by a            C-RNTI or a CS-RNTI (if configured), RA-RNTI, TC-RNTI,            P-RNTI, SI-RNTI;        -   an indication by higher layer parameter dci-Format2-0 to            monitor one or two PDCCH candidates for DCI format 2_0 and a            corresponding CCE aggregation level;        -   an indication by higher layer parameter dci-Format2-1 to            monitor PDCCH candidates for DCI format 2_1;        -   an indication by higher layer parameter dci-Format2-2 to            monitor PDCCH candidates for DCI format 2_2;        -   an indication by higher layer parameter dci-Format2-3 to            monitor PDCCH candidates for DCI format 2_3;        -   if search space set is a UE-specific search space set, an            indication by higher layer parameter dci-Formats to monitor            PDCCH candidate either for DCI format 0_0 and DCI format            1_0, or for DCI format 0_1 and DCI format 1_1.

For sake of completeness, reference is made to technical specification3GPP TS 38.331 (referenced above) in section 6.3.2 titled, “Radioresource control information element” specifies, thereof, which definesthe Search Space information element, termed “SearchSpace IE.”

Benefits of the Present Disclosure

In the context of the present disclosure, the inventors have recognizedthat it is beneficial for mobile terminals to know whether or not it isintended, at a specific time instant, to monitor a set of PDCCHcandidates in one or more control resource sets (CORESETs). Thisknowledge may help the mobile terminal to decide, at this time instant,whether or not it can skip monitoring control resource sets (CORESETs).

For conveying this knowledge to mobile terminals, the present disclosuremakes readily use of the fact that the PDCCH is signaled in abeam-forming manner. In this regard, not only the PDCCH but also thedemodulation reference signals (DMRS) are transmitted using beam-formingmechanisms. However, the presently used beam-forming is transparent tothe mobile terminals, and hence does not permit such benefits.

To circumvent this, one general concept of the present disclosure is toprovide an association between demodulation reference signal sequencesand transmission beams such that each mobile terminal can restrict itsprocessing to demodulation reference signals which are specific to theirtransmission beams only.

Should a mobile terminal find out that the processing with only thosedemodulation reference signals that are specific to their transmissionbeam is unsuccessful, then it can skip any further monitoring of thePDCCH candidates in the one or more control resource sets (CORESETs).This facilitates the mobile terminal to substantially reduce itsprocessing load, especially (but not exclusively) when operating in anunlicensed spectrum.

Generic Scenario

In the following, mobile terminals, base stations, and procedures tomeet these needs will be described in relation to the new radio accesstechnology envisioned for the 5G mobile communication systems, but whichmay also be used in LTE mobile communication system. Differentimplementations and variants will be explained as well. The followingdisclosure has been facilitated by the discussions and findings asdescribed above and may for example be based at least on part thereof.

In general, it should be noted that many assumptions have been madeherein so as to be able to explain the principles underlying the presentdisclosure in a clear and understandable manner. These assumptions arehowever to be understood as merely examples made herein for illustrationpurposes that should not limit the scope of the disclosure. A skilledperson will be aware that the principles of the following disclosure andas laid out in the claims can be applied to different scenarios and inways that are not explicitly described herein.

Moreover, some of the terms of the procedures, entities, layers etc.,used in the following are closely related to LTE/LTE-A systems or toterminology used in the current 3GPP 5G standardization, even thoughspecific terminology to be used in the context of the new radio accesstechnology for the next 3GPP 5G communication systems is not fullydecided yet.

Thus, terms could be changed in the future, without affecting thefunctioning of the embodiments. Consequently, a skilled person is awarethat the embodiments and their scope of protection should not berestricted to particular terms exemplarily used herein for lack of neweror finally agreed terminology but should be more broadly understood interms of functions and concepts that underlie the functioning andprinciples of the present disclosure.

FIG. 1 illustrates a block diagram of a wireless communication systemincluding a mobile terminal 110 (also referred to as user equipment,UE), and a base station 160 (also referred to as g Node B, gNB). Themobile terminal 110 comprises processing circuitry 130 and a transceiver120 which are indicated as separate building blocks in the diagram.Similarly, the base station 160 comprises processing circuitry 180 and atransceiver 170 which are indicated as separate building blocks in thediagram.

FIG. 2 is an exploded view of the separate building blocks of FIG. 1,and depicts implementation specific circuitry of the mobile terminal 110and of the base station 160 included in the wireless communicationsystem.

For ease of understanding, this figure has been simplified to only showcircuitry which is related to downlink control channel receptions. Thisshall, however, not be understood as imposing any limitations upon thefunctionality of the mobile terminal 110 and the base station 160 of thewireless communication system.

In more detail, the mobile terminal 110 in FIG. 2 comprises again thetransceiver 120 and processing circuitry 130. Importantly, theprocessing circuitry 130 comprises a demodulation circuitry 130-1,descrambling circuitry 130-2, and a decoding circuitry 130-3, andadditionally comprises a radio channel estimation circuitry 130-4, ademodulation reference signal (also referred to as DM-RS) generationcircuitry 130-5 and an association storage circuitry 130-6.

Further, the base station 160 in FIG. 2 comprises again the transceiver170 and the processing circuitry 180. Importantly, the processingcircuitry 180 comprises a coding circuitry 180-1, a scrambling circuitry180-2, a modulation circuitry 180-3, and also an association storagecircuitry 180-5, and a demodulation reference signal (DM-RS) sequencegeneration section 180-4.

In general the following description assumes that the mobile terminal110 and the base station 160 engage in downlink communication with eachother via beams. For downlink transmissions, the base station 160 isconfigured with a plurality of transmission beams (tx-beam #1, tx-beam#2, tx-beam #3, . . . ), which have different directivities and/orcoverage. Equally, the mobile terminal 110 is configured with aplurality of reception beams (rx-beam #1, rx-beam #2, rx-beam #3, . . .) which also have different directivities and/or coverage.

Well established procedures for beam management serve the purpose ofestablishing an initial beam pair, serve the purpose of adjusting thebeam pair during normal operation, and serve the purpose of recoveringthe beam pair after beam failure. Importantly, the beam pair identifiesa pair comprising one transmission beam (e.g., tx-beam #1) of the basestation 160 and a reception beam (e.g., rx-beam #1) of the mobileterminal 110 for the downlink communication.

Such a beam pair may identify a pair of transmission and reception beamswhich have opposite directivity and/or coverage, i.e., beams which arephysically pointing directly at each other. However, this does notalways result in good connectivity. Due to obstacles in the surroundingenvironment, such a direct path between transmitter and receiver may beblocked, and a reflected path may provide better connectivity.

In the context of the present disclosure, it is important to understandthat the mobile terminal 110 is aware of such a beam pair orcorrespondence between transmission beam (e.g., tx-beam #1) andreception beam (e.g., rx-beam #1) which has proven suitable for carryingdownlink communication. In other words, this correspondence may entail adirect path or a reflected path of radio wave propagation.

Now, when referring to downlink control channel (also referred to asphysical downlink control channel, PDCCH) receptions, one aspect in thepresent disclosure is that the mobile terminal, in particular itsprocessing circuitry 130, has an assumption on (exactly) which one ofits plural transmission beams will be used by the base station fordownlink transmissions.

The processing circuitry 130 may infer this assumption from (successful)downlink transmissions in the past. Notably, there is no necessity torestrict the present disclosure only to ongoing downlink transmissions.Rather, the processing circuitry 130 can also infer the assumption incase of an initial beam establishment and/or in case of a beam failurerecovery.

In any case, the mobile terminal 110 signals to the base station 160 thetransmission beam which permits the transceiver 120 to detect a highestreception power and/or reception quality. Also in this case, theprocessing circuitry 130 can reasonably assume that the base stationrelies on this signaled transmission beam for subsequent downlinkcommunication.

In short, there exist numerous scenarios where the processing circuitry130 of the mobile terminal 110 has an assumption regarding which one ofthe plurality of transmission beams (e.g., tx-beam #1) the base station160 is configured to use for downlink control channel (also referred toas physical downlink control channel, PDCCH) and correspondingdemodulation reference signal (DM-RS) transmissions.

With this assumption, the transceiver 120 of the mobile terminal 110performs receptions, namely by using one of its plurality of receptionbeams (e.g., rx-beam #1) which is corresponding to the assumed one ofthe plural transmission beams of the base station 160. As discussedabove, this correspondence entails a pair of beams which are physicallycorresponding to each other, or which are (already) found to resemblethe best correspondence.

Having received the demodulation reference signal, the processingcircuitry 130 of the mobile terminal 110, performs radio channelestimation based thereon. This may be performed e.g., in the radiochannel estimation circuitry 130-4.

By way of example, 5G NR is carrying demodulation reference signalsspecifically associated with a downlink control channel to permitcoherent demodulation of the corresponding control channel candidates.For this purpose, the received demodulation reference signal, to be usedfor channel estimation, corresponds to the received downlink controlchannel candidate to be demodulated as discussed below.

This correspondence between demodulation reference signal and downlinkcontrol channel candidate may result from a neighboring location in timeand frequency where both are transmitted.

By way of example, 5G NR prescribes such neighboring location in that itmaps the demodulation reference signals onto every fourth subcarrier ina resource element group, REG. A set of plural REGs is defined as a REGbundle across which precoding is constant. Thus, channel estimation isperformed per REG bundle, at least one of which forms the controlresource set (CORESET).

Further, the mapping of the physical downlink control channel PDCCHcarrying coded and modulated downlink control information DCI is subjectto a certain structure, based on control channel elements, CCEs, andsame resource element groups, REGs. A PDCCH is transmitted using 1, 2,4, 8, or 16 contiguous control channel elements which are defined asaggregation levels. The control channel element is the unit in terms ofwhich the search spaces are defined.

In particular, a search space is a set of downlink control channelcandidates formed by CCEs at a given aggregation level, which the mobileterminal attempts to decode. At a configured monitoring occasion for asearch space, the mobile terminal will attempt to decode the downlinkcontrol channel candidates, the number of which is configured per searchspace (and thus also per aggregation level).

The radio channel estimation is performed by the processing circuitry130 using a demodulation reference signal sequence which is (separately)generated at the mobile terminal. In particular, the processingcircuitry 130 may use a sequence which is generated in the DM-RSsequence generation circuitry 130-5.

By way of example, in 5G NR the demodulation reference signals for thedownlink control channel are generated using a higher layer parameterpdcch-DMRS-SramblingID, if provided, or by the physical layer cellidentity (see e.g., TS38.211, section 7.4.1.3.1). These parameters areused to initialize a pseudo-random sequence generator, where thegenerated pseudo-random sequence c(i) defines the reference-signalsequence r₁(m) for OFDM symbol 1.

The processing circuitry 130 generates the demodulation reference signalsequence observing (complying with, taking into account) an associationwhich associates it with the assumed one of the plurality oftransmission beams. In other words, this association directly influenceswhich demodulation reference signals sequence is generated.

In an exemplary configuration, this association can be provided tomobile terminals via higher layer signaling, e.g., via radio resourcecontrol, RRC, configuration, or system information signaling, or may beinferred at each mobile terminal separately, e.g., derived from thesynchronization signal block (SSB) index each of which identifies aseparate one of the plurality of transmission beams of the base station.

Considering for example a specific assumed transmission beam, theassociation may directly associate this assumed transmission beam withthe generated demodulation reference signal sequence. Also, theassociation may associate the assumed transmission beam with a sequence(also termed base sequence) on the basis of which the demodulationreference signal sequence is generated. Then, the association mayindirectly associate this assumed transmission beam with the generateddemodulation reference signal sequence.

The association may be stored in an association storage circuitry 130-6and is shown, for example, in FIG. 3, where each of the plurality oftransmission beams is associated with a different demodulation referencesignal (DM-RS) generating base sequence, and thus indirectly associatedwith the generated demodulation reference signal sequence.

For compatibility reasons, the exemplarily shown DM-RS generating basesequence is defined to include 16 bits, thereby reusing the format ofthe parameter specified in 5G NR that initializes the pseudo-randomsequence generator. This shall however not be understood as limiting thepresent disclosure.

In any case, the association is defined to ensure that at least two ofthe plurality of transmission beams are associated with differentdemodulation reference signal sequences. In other words, there exist twotransmission beams, for which the processing circuit 130—when observingthe association—will generate two different demodulation referencesignal sequences.

Consequently, the association prescribes that the processing circuit 130will generate different demodulation reference signal sequencesdepending on which one of the plural transmission beams it considers asthe assumed transmission beam. Observing such an association, theprocessing circuitry 130 performs an improved channel estimation.

The processing circuitry 130 performs a channel estimation whichconsiders a demodulation reference signal which is specific to thetransmission using the assumed transmission beam. This assumedtransmission beam is the beam which has proven good connectivity for themobile terminal 110.

Other mobile terminals will likely consider other assumed transmissionbeams. Accordingly, these other mobile terminals will receivedemodulation reference signals which are specific to transmissions usingtheir assumed transmission beams, and which have proven goodconnectivity for them.

The channel estimation performed by the processing circuitry 130 can,when observing the association, already at a very early stage of thedownlink control channel reception permit the mobile terminal 110 toknow whether or not the received demodulation reference signal isactually intended for itself or not. This permits the mobile terminal topossibly skip any further processing of downlink control channelcandidates associated with this demodulation reference signal.

In more detail, assuming for example that the demodulation referencesignal was not intended for the mobile terminal 110, the channelestimation performed by the processing circuitry would be based on ademodulation reference signal that was generated by the base station 160in association with a different transmission beam than the demodulationreference signal sequence generated by the mobile terminal 110.

In an exemplary implementation, the processing circuitry 130(cross-)correlates the received demodulation reference signal (DM-RS)with the generated demodulation reference signal sequence, and theprocessing circuitry 130 then determines a radio channel estimationquality based on the correlation result, and in case the radio channelestimation quality is below a threshold, the processing circuitry 130does not demodulate the received downlink control channel candidate.

As the association prescribes that at least two of the plurality oftransmission beams are associated with different demodulation referencesignal sequences, this may result in a channel estimation which isaccordingly using a different demodulation reference signal sequence ascompared to that which was used by the base station 160 to perform thedemodulation reference signal transmission. And such a differencebetween the sequences will result in the processing circuitry estimatinga poor (inferior, bad) quality of the radio channel.

In other words, the channel estimation quality is a sufficient indicatoron which the further processing of the corresponding downlink controlchannel candidates may depend. For example, by simply discarding poorradio channel quality estimations, the mobile terminal can possibly skipany further processing of downlink control channel candidatescorresponding to this demodulation reference signal. Thereby, also theprocessing load for the mobile terminal is reduced.

When the mobile terminal 110 performs channel estimation based on areceived demodulation reference signal which was actually intended forthe mobile terminal, the processing circuitry 130 determines asufficient (superior, good) radio channel estimation quality (unless thechannel is otherwise disturbed).

Using this radio channel quality, the processing circuitry 130 of thismobile terminal 110 then demodulates the received downlink controlchannel candidate, which is corresponding to the received demodulationreference signal. For this demodulation, the processing circuitry 130uses the radio channel estimation. The demodulation may be performed inthe demodulation circuitry 130-1.

Again, the processing circuitry 130 performs the demodulation notindependent of the outcome of the channel estimation. Rather, thedemodulation is being performed by the processing circuitry 130depending on the channel estimation quality. Hence, it can be ensuredthat demodulation reference signal transmissions which are not intendedfor the mobile terminal are not used by the processing circuitry 130during modulation.

Only for the sake of completeness, it shall be mentioned that the mobileterminal 110 may also include a descrambling circuitry 130-2, and adecoding circuitry 130-3 which performs the blind decoding of therespective search spaces. These circuitries are being sequentiallyoperated should the demodulation using the radio channel estimation besuccessful.

Similarly to the above, the base station 160 is also operating based onan association.

Here the processing circuitry 180 of the base station 160 assumes thatthe mobile terminal is configured to use for downlink control channel(abbrev. as PDCCH) and corresponding demodulation reference signal(DM-RS) receptions at the mobile terminal one of a plurality ofreception beams (rx-beam #1).

The transceiver 170 of the base station 160 transmits a downlink controlchannel and corresponding demodulation reference signal to the mobileterminal using one of a plurality of transmission beams (tx-beam #1)corresponding to the assumed one of the plurality of reception beams(rx-beam #1).

The processing circuitry (160), in operation, modulates the downlinkcontrol channel (PDCCH) to be transmitted and generates a demodulationreference signal sequence to be transmitted as the correspondingdemodulation reference signal (DMRS).

The demodulation reference signal sequence is generated observing anassociation which is associating the generated sequence with the one ofthe plurality of transmission beams (tx-beam #1) such that at least twoof the plurality of transmission beams are associated with differentdemodulation reference signal sequences.

First Exemplary Association

In connection with the above, an association is described whichprescribes that at least two of the plurality of transmission beams areassociated with different demodulation reference signal sequences. Thereare numerous mechanisms to define such an association. Further, it hasbeen discussed that the association may directly or indirectly associatethe transmission beams with the generated demodulation reference signalsequence.

In the following, a first exemplary association is described whichindirectly associates the transmission beams with different demodulationreference signal sequences. An implementation of such an exemplaryassociation is depicted in FIG. 4. In particular, the association isdefined with regard to DM-RS generating base sequences (or modifiedscrambling-ID) which in turn are to be used for generating thedemodulation reference signal sequences.

In other words, in this example, the processing circuitry 130 generatesthe demodulation reference signal sequence from a base sequence whichincludes: an identification of the assumed one of the plurality oftransmission beams (tx-beam ID), such that the generated demodulationreference signal sequence is associated with the assumed one of theplurality of transmission beams (tx-beam #1).

With such a definition of the association, it can be ensured that atleast two of the plurality of transmission beams are associated withdifferent demodulation reference signal sequences.

For example, a base sequence (or modified scrambling-ID) additionallyincludes at least one of: at least a part of an identification of thecell (Cell-ID) comprising the assumed transmission beam, and at least apart of an identification of the network (PLMN-ID) comprising the cell.The at least parts of the identification of the cell or of the networkmay correspond to a predetermined number of least significant bits ofthe respective identification.

Note that the Cell-ID, PLMN-ID or beam ID can also impact the basesequence in an indirect way, e.g., base sequence (or modifiedscrambling-ID) can also be derived based on a first number generatedfrom PLMN-ID, a second number generated from Cell ID and a third numbergenerated from beam ID, where at least one of the numbers is shorterthan the original length of Cell ID, PLMN ID or beam ID.

With this addition of at least parts of the Cell-ID and PLMN-ID to theDM-RS generating base sequence, conflicts resulting from the sameassociations between neighboring cells and/or networks can be prevented.

In other words, generating the association deterministically (e.g., notrandomly) always bears the risk that for two base stations inneighboring cells and neighboring networks, the same demodulationreference signal sequence is generated for a same transmission beam.With these additions, conflicts can be prevented.

Taking for example, the first row in FIG. 4, the association specifiesthat the transmission beam #0 is associated with a base sequence whichincludes, as beam identification the value ‘011 001.’ Further, the basesequence includes, as part of the cell identification the value ‘10101.’Finally, the base sequence also includes, as part of the networkidentification, the value ‘00101.’

In 5G NR, the PLMN ID is defined to require minimum 7 bits and maximum20 bits, and the Cell ID is defined to require 10 bits. In order toarrive at a total of 16 bits, the identification values are truncatedsuch that each comprises 5 bits. This is shown in FIG. 5a . Alternativecompositions of the base sequence are shown in FIG. 5b , where only theCell ID is truncated to 3 bits, and the minimum of 7 bits of the PLMN IDis reused, and in FIG. 5c , where the PLMN ID is (completely) discarded,and the Cell ID is reused with its total length of 10 bits. The lattercase shown in FIG. 5c is suitable, for example, for licensed bandoperation with only one operator (and hence only one PLMN ID) in thegiven area. On the other hand, the case in FIG. 5b is suitable for thescenario where only a few cells are deployed in the given area. The casein FIG. 5a provides the trade-off between the number of distinguishablecells and number of distinguishable networks. Alternatively, in casewhere the PLMN ID is not available, the fixed value, e.g., 0, can beused in the corresponding bit field of the base sequence.

This exemplary implementation can be combined with ascrambling/descrambling of the downlink control channel.

According to a further exemplary implementation, the processingcircuitry 130 de-scrambles the demodulated downlink control channelcandidate using the base sequence in the mobile terminal. Similarly, theprocessing circuit 180 scrambles the downlink control channel to bemodulated using the base sequence in the base station. This furtherenhances the separation.

Second Exemplary Association

A second exemplary association is disclosed which indirectly associatesthe transmission beams with different demodulation reference signalsequences.

This implementation builds on the general understanding that first thedemodulation reference signal sequence is derived in the conventionalfashion (e.g., higher layer parameter pdcch-DMRS-SramblingID, ifprovided, or physical layer cell identity). Then, the sequence issubjected to orthogonal cover codes which are associated with thedifferent transmission beams.

In other words, the processing circuitry 130 generates the demodulationreference signal sequence from a base sequence corresponding to ascrambling identification, scrambling-ID, including using an orthogonalcover code which is associated with the assumed one of the plurality oftransmission beams (tx-beam #1).

With such a definition of the association, it can be ensured that atleast two of the plurality of transmission beams are associated withdifferent demodulation reference signal sequences. Additionally, thisenhances the separation of different beams.

This exemplary implementation can be combined with ascrambling/descrambling of the downlink control channel.

According to a further exemplary implementation, the processingcircuitry 130 de-scrambles the demodulated downlink control channelcandidate using the base sequence in the mobile terminal. Similarly, theprocessing circuit 180 scrambles the downlink control channel to bemodulated using the base sequence in the base station. This furtherenhances the separation.

Third Exemplary Association

A third exemplary association is disclosed which indirectly associatesthe transmission beams with different demodulation reference signalsequences.

This implementation builds on the general understanding that first thedemodulation reference signal sequence is derived in the conventionalfashion (e.g., higher layer parameter pdcch-DMRS-SramblingID, ifprovided, or physical layer cell identity). Then, the sequence iscyclically shifted based on different shift values which are associatedwith the different transmission beams.

In other words, the processing circuitry 130 generates the demodulationreference signal sequence from a base sequence corresponding to ascrambling identification, scrambling-ID, including applying a cyclicshift to the demodulation reference signal sequence corresponding to acyclic shift value which is associated with the assumed one of theplurality of transmission beams (tx-beam #1).

Again, this exemplary implementation can be combined with ascrambling/descrambling of the downlink control channel.

According to a further exemplary implementation, the processingcircuitry 130 de-scrambles the demodulated downlink control channelcandidate using the base sequence in the mobile terminal. Similarly, theprocessing circuit 180 scrambles the downlink control channel to bemodulated using the base sequence in the base station. This furtherenhances the separation.

First Exemplary Embodiment

FIG. 6 illustrate a flow diagram of downlink control channel (PDCCH)receptions according to a first exemplary embodiment, whereas FIG. 7shows a time diagram of such downlink control channel receptions.

This first exemplary embodiment exploits the general concept forreceiving downlink control channel transmissions scheduling a randomaccess response message on a downlink shared channel as shown in FIG. 7.

As this embodiment is closely linked to the random access procedure asspecified in 5G NR, the according terminology is used in the following.This, however, shall not be understood as limiting the presentdisclosure in any respect.

The embodiment, for example, builds on the understanding that the UE (ormobile terminal) is carrying out a random access procedure, and in thiscontext expects to receive a demodulated PDCCH candidate which isincluded in a common search space carrying downlink control information(DCI). Due to the association discussed before, the downlink controlinformation (DCI) is intended for (only) a group of plural mobileterminals, and the downlink control information (DCI) corresponds to atleast DCI-Format 1-0 with a CRC scrambled with a random access radionetwork temporary identifier (RA-RNTI).

In more detail, the UE determines (S61—FIG. 6) an assumed transmissionbeam, e.g., beam #1 which is suitable for communication with the gNB.For example, the UE can measure the reception power or reception qualityof a Primary Synchronization Signal PSS or a Secondary SynchronizationSignal SSS included in the SS block (SSB). Since the SSB is transmittedby the gNB in a beam sweeping manner, it can derive the SSBidentification, and therewith, the beam ID which has proven suitable.This beam ID is henceforth considered to be the assumed transmissionbeam.

On this basis, the UE can already proceed to generate a DM-RS sequenceassociated with the assumed transmission beam, e.g., beam #1. For thisgeneration, the UE observes (complies with, takes into account) theassociation, which associates the generated sequence with the assumedtransmission beam, e.g., beam #1. With this association at least two ofthe plurality of transmission beams are associated with different DM-RSsequences. Alternatively, the UE can generate the sequence also at alater stage.

Then, the UE sends (S63—FIG. 6) a random access channel (RACH) preamblecorresponding to the assumed transmission beam e.g., beam #1. In moredetail, different RACH preambles and/or RACH resources are defined in 5GNR to convey the information of the best suitable (or assumed)transmission beam to the gNB. Thereby, the UE ensures that the gNB canalso determine the transmission beam for subsequent transmissions to theUE.

Subsequently, the UE prepares (S64—FIG. 6) for receiving a random accessresponse RAR message. The random access response message is transmittedby the gNB on the PDSCH and is scheduled by means of a PDCCHtransmission on a corresponding common search space, e.g., Type1-PDCCHcommon search space set. This common search space set corresponds to aconfigured location in time and frequency, e.g., the first two symbolsin every slot.

For the duration of the RAR window, the UE monitors (S65—FIG. 6) PDCCHtransmissions for the RAR message corresponding to the RACH preamble.However, unlike the ordinary procedure, the UE carries out the improvedPDCCH receptions discussed above, thereby reducing the processing loadof the UE.

In particular, the UE performs (S66—FIG. 6) channel estimation based onreceived DM-RS for the PDCCH. This channel estimation uses the generatedDM-RS sequence from before. As this generated DM-RS sequence isassociated with the assumed transmission beam, e.g., beam #1, thechannel estimation quality is poor (S67—FIG. 6) except for the receivedDM-RS which is also transmitted on the assumed transmission beam, e.g.,transmission beam.

In case the channel estimation quality is found to be poor, the UE skips(S68—FIG. 6) the PDCCH decoding for the common search space set in thisslot and directly proceeds to prepare for receiving PDCCH scheduling inthe next slot. Thereby, the processing load can be significantly reducedin the UE.

In case the channel estimation quality is found to be sufficient, the UEperforms (S69—FIG. 6) PDCCH decoding of PDCCH candidates of the commonsearch space set. Although not depicted, the UE first demodulates eachPDCCH candidate using the channel estimation.

Having decoded the PDCCH with the scheduling, the UE can subsequentlyreceive (S70—FIG. 6) the RA response message via PDSCH.

As apparent from FIG. 7, the gNB combines the RAR messages fromdifferent UEs to thereby ensure a faster response time. In the depictedcase, UE1 and UE2 are performing the random access channel procedure ata similar point in time. Thus, the gNB transmits a RAR message at thesame time.

Since UE1 and UE2 are having different assumed transmission beams, e.g.,beam #2 and beam #1 respectively, the association can ensure that onlythe UE1 and not the UE2 is decoding the PDCCH in the slot correspondingto beam #2, and that only the UE2 and not the UE1 is decoding the PDCCHin the slot corresponding to beam #1.

Second Exemplary Embodiment

FIG. 8 depicts a flow diagram of downlink control channel (PDCCH)receptions according to a second exemplary embodiment whereas FIG. 9shows a timing diagram of such downlink control channel receptions.

This second exemplary embodiment considers an unlicensed (NR-U)scenario, in particular where the channel occupation time (COT) conceptis deployed as shown in FIG. 9.

As discussed before, the channel occupation time defines a maximumtransmit duration during which an entity is transmitting on a givencarrier without re-evaluating the availability of that carrier (i.e.,LBT/CCA). This concept can be readily deployed for NR-U andadvantageously combined with the improved PDCCH receptions.

In more detail, the UE receives (S80—FIG. 8) the configuration ofmonitoring locations for COT indications.

This configuration can be exemplarily received via higher layersignaling, e.g., RRC. The monitoring locations can be understood ascommon search space sets carrying DCIs, for example of DCI-Format 2_0,which are conveying an indication of a COT structure including anindication of the COT duration and of the transmission format, such asDL, UL and flexible symbols. As an example, the indication in DCI canpoint to an entry of a table which defines multiple possible structuresof the COT.

Subsequently, the UE determines (S81—FIG. 8) an assumed transmissionbeam, generates (S82—FIG. 8) a DM-RS sequence associated with thisassumed transmission beam, and performs (S83—FIG. 8) channel estimationusing the generated DM-RS sequence to determine whether or not thechannel estimation quality is poor (S84—FIG. 8)

In case a poor channel estimation quality (S84—FIG. 8) is determined forthe UE's assumed transmission beam, and this occurs at current timeinstant which is not corresponding to such a COT indication monitoringlocation (S86—FIG. 8) the UE skips the decoding of PDCCH at the currenttime instant until the next configured time instant corresponding to thenext monitoring location of COT indication.

In case a poor channel estimation quality (S84—FIG. 8) is determined forthe UE's assumed transmission beam, and the current time instant is atime instant which is corresponding to a COT indication monitoringlocation (S86—FIG. 8), the UE performs channel estimation also using adifferent DM-RS sequence associated with another transmission beam(S87—FIG. 8), e.g., not the serving beam of the UE. Channel estimationis performed (S88—FIG. 8) as long as the maximum number of beam trialsis reached.

Should one of the channel estimations with DM-RS associated with othertransmission beams result in a suitable channel estimation quality, theUE performs (S85—FIG. 8) PDCCH decoding and then follows the COTstructure of the indication. From this COT structure, the UE can inferthe COT duration, and then skips PDCCH receptions during the entire COTduration.

In other words, the UE assumes that every transmission from the gNB iscomplying with the COT, and thus can be only present when it decodes aCOT indication at the configured monitoring locations.

Then, should the channel estimation result in a poor channel estimationquality for another transmission beam (not the serving beam of the UE),it knows that all transmissions by the gNB during the entire COTduration are not intended for the UE but for a different UE, thus it canskip monitoring until the end of the COT structure. Thereby, theprocessing load at the UE is significantly reduced.

Third Exemplary Embodiment

FIG. 10 depicts a flow diagram of downlink control channel (PDCCH)receptions according to a third exemplary embodiment whereas FIG. 11shows a timing diagram of such downlink control channel receptions.

This third exemplary embodiment considers an unlicensed (NR-U) scenario,in particular where the channel occupation time (COT) concept isdeployed, and where the beam specific transmissions by the gNB arepreceded by a beam-common preamble (i.e., a preamble which istransmitted on every one of the plurality of transmission beams of thegNB) as illustrated in FIG. 11.

Such a beam common preamble can ensure compatibility of NR-U with othertechnologies in an unlicensed band and further improve the reliabilityof the COT detection by the UEs even under adverse propagationconditions.

In more detail, the UE receives (S100—FIG. 10) a configuration ofmonitoring locations for channel occupation time (COT) indicationsincluding a beam common preamble sequence at configured monitoringlocations.

This configuration can be exemplarily received via higher layersignaling, e.g., RRC. The monitoring locations can be understood ascommon search space sets carrying DCIs, for example of DCI-Format 2_0,which are conveying an indication of a COT structure including anindication of the COT duration and of the transmission format, such asDL, UL and flexible symbols. As an example, the indication in DCI canpoint to an entry of a table which defines multiple possible structuresof the COT.

At such a configured preamble monitoring location, the UE attempts todetect (S101—FIG. 10) the beam-common preamble sequence.

This detection does not necessarily include any PDCCH monitoring butinstead can also result from power measurements at the configuredlocation. Also different mechanism can be envisioned, for example,mechanisms which rely on a dedicated circuit configured for the solepurpose of detecting such preambles.

In case a preamble is detected (S102—FIG. 10), the UE proceeds to carryout the process which has already been described in connection with thesecond exemplary embodiment. For reasons of brevity, reference is onlymade to the according description of the individual steps in FIG. 8.

In case no preamble is detected (S102—FIG. 10), the UE skips thedecoding of PDCCH at the current time instant until the next configuredtime instant. Thereby, the processing load at the UE is significantlyreduced.

FIG. 12 depicts a flow diagram of downlink control channel (PDCCH)transmissions according to the third exemplary embodiment. This figurereflects the processing by the gNB.

In more detail, the gNB first performs (S121—FIG. 12) clear channelassessment (CCA) in unlicensed operation. If CCA is passed (S122—FIG.12), the gNB sends (S123—FIG. 12) COT preamble using a beam-commonsequence at the first available time instant configured in the UEs. Thistime instant may, for example, correspond to the first OFDM symbolimmediately after CCA. At the symbol(s) immediately following the COTpreamble, the gNB transmits (S124—FIG. 12) beam specific PDCCH withcorresponding beam specific DM-RS signals.

With the PDCCH transmission, the gNB may schedule (S125—FIG. 12)downlink and uplink data transmission for the intended UE(s) during theCOT. When the gNB finds that the COT duration elapsed (S126—FIG. 12),the gNB releases (S127—FIG. 12) the channel, e.g., the gNB performs nofurther transmissions.

Another Exemplary Implementation

FIGS. 13 and 14 depict a flow diagram and a timing diagram of the mobileterminal and the base station according to another exemplaryimplementation. In this implementation the concepts previously discussedare further refined and permit a reduction of processing load even formobile terminals which are intended to be addressed within a channeloccupation time (COT) duration.

In this context, it is the general understanding that the mobileterminal is provided with information specifying a configuration ofusage patterns for the channel by the base station. Such usage patternscan, for example, be a channel occupation time (COT) structure as shownin FIG. 14. However, the usage patterns shall not be understood as beingrestricted in this respect as there are more possibilities ofconfiguring the channel usage.

For example, a substantial constraint for the base station results fromthe fact that the channel occupation time (COT) structure presently doesnot permit attributing different time periods (e.g., slots) within theCOT duration to individual beam usages. To remedy this deficiency, it ispossible to define the usage pattern as including an individual durationfor each beam usage. This permits a more flexible scheduling.

Again, this is different from the COT structure. The COT structuremerely identifies the COT duration and the transmission format (DL, ULor flexible symbols) to be used for the entire COT duration. In otherwords, within the COT duration included in the COT structure the basestation will rely on dynamic scheduling via the downlink control channelfor attributing different time periods to individual mobile terminals.

And with the dynamic scheduling, each mobile terminal, unless excludedfrom any receptions during the COT duration, will have to monitor thedownlink control channel for downlink control channel candidates anddemodulation reference signal transmissions which are transmitted usingthe assumed (serving) transmission beam.

For this purpose, new downlink control information (DCI) is definedwhich is to be transmitted by the base station in a search space whichis common to a group of plural mobile terminals. The DCI includes atleast a time duration for which the DCI is held to be valid, and anidentification of the usage pattern which may include an individualduration for each beam usage. Optionally, it may also include anidentification of the cell (Cell-ID) and/or at least a part of anidentification of the network (PLMN-ID).

This usage pattern, in the context of the present disclosure, is definedas an identification of at least one of the plurality of transmissionbeams (tx-beam #1) which is being used by the base station for downlinkcontrol channel candidate (PDCCH candidate) and a correspondingdemodulation reference signal (DM-RS) transmissions during at least apart of the time duration.

For example, in case the new downlink control information (DCI) includesan identification of two transmission beams, e.g., tx-beam #1 andtx-beam #2 then this downlink control information also includes anindication of the individual usage of each beams within the timeduration for which the downlink control information is held to be valid.

In general, the usage pattern prescribes the transmission beams to beused for the control channel within the time duration for which thedownlink control information is held to be valid, and thereby restrictscontrol channel transmissions to only those mobile terminals for whichthe prescribed transmission beams facilitate a suitable channelestimation quality. As the downlink control channel is responsible forscheduling, the prescribed transmission beams accordingly restrict thecommunication to only specific mobile terminals.

Notably, this implementation also prescribes a specific signalingmechanism for transmission of the new downlink control information (newDCI) with the usage pattern. Rather than performing a downlink controlchannel transmissions in a conventional manner with different (narrow)beams with different directivity and/or coverage, the present disclosureforesees that the DCI is carried in a downlink control channel which istransmitted by the base station on a wide transmission beam.

This wide transmission beam is not intended to replace the different(narrow) transmission beams in the wireless communication system.Rather, it has been recognized by the inventors that the transmission ofdownlink control channels on common search spaces with different(narrow) transmission beam results in a complicated system design.

In this respect it is proposed to configure the base station with asingle wide transmission beam (e.g., sector beam or omni-directionalbeam) which can convey downlink control channel transmission on commonsearch spaces to multiple mobile terminals more easily. For example, thebase station could be configured to include one wide transmission beam,e.g., beam #0, and plural (narrow) transmission beams, e.g., tx beams#1-#31

In the following, this wide beam usage for downlink control channeltransmissions is said to use a specific format for the downlink controlchannel (PDCCH) transmissions. The specific format shall be understoodas the format for carrying the new downlink control channel information(DCI) discussed above. Downlink control information (DCI) is generallyconveyed using specific formats, thereby enabling an easy identificationand decoding by the mobile terminal. This equally applies to the presentcase.

In an exemplary embodiment, the base station is configured to usespecific time instances for a specific format of downlink controlchannel (PDCCH) and corresponding demodulation reference signal (DM-RS)transmissions to the mobile terminal with a specific wide transmissionbeam (tx-beam #0) which is different from the plurality of transmissionbeams. And the mobile terminal's processing circuitry is provided withinformation specifying said configuration.

Subsequently, the mobile terminal's transceiver receives (S130—FIG. 13)at a specific time instant (S131—FIG. 13) a downlink control channelcandidate (PDCCH candidate) and a corresponding demodulation referencesignal (DM-RS) of the specific format from the base station using one ofthe plurality of reception beams (rx-beam #0) suitable for receiving thespecific wide transmission beam (tx-beam #0).

Then, the mobile terminal's processing circuitry performs (S133—FIG. 13)radio channel estimation based on the received demodulation referencesignal (DM-RS) and, depending on a radio channel estimation quality,demodulates the downlink control channel candidate (PDCCH candidate)using the radio channel estimation, and decodes the demodulated downlinkcontrol channel candidate according to the specific format.

The specific format prescribes the decoded downlink control channelcandidate to carry downlink control information including: a timeduration for which the downlink control information is held to be valid,and an identification of at least one of the plurality of transmissionbeams (tx-beam #1) which is being used by the base station for downlinkcontrol channel candidate (PDCCH candidate) and a correspondingdemodulation reference signal (DM-RS) transmissions during at least partof the time duration.

Finally, the mobile terminal's processing circuitry uses theidentification (S134-FIG. 13) of at least one of the plurality oftransmission beams (tx-beam #1) to generate demodulation referencesignal sequences observing the association which are to be used(S135—FIG. 13) for performing channel estimation during the least partof the time duration for which the downlink control information is heldto be valid.

Importantly, the mobile terminal's processing circuitry may also detectthat the identification (S134—FIG. 13) of at least one of the pluralityof transmission beams (tx-beam #1) does not include a suitabletransmission beam for the mobile terminal to receive (e.g., not theassumed transmission beam). Then, the mobile terminal's processingcircuitry skips (S136—FIG. 13) further monitoring of downlink controlchannels within the time duration for which the downlink controlinformation element is held to be valid.

As already mentioned above, it is advantageous to attributing differenttime periods (e.g., slots) within the COT duration to individual beamusages. In this case, the processing load can be even reduced for mobileterminals which are intended to be addressed within the COT duration.

Further Aspects

According to a first aspect, a user equipment is provided, comprising aprocessing circuitry and transceiver. The processing circuitry assumesthat a base station is configured to use for downlink control channel(PDCCH) and corresponding demodulation reference signal (DM-RS)transmissions to the mobile terminal one of a plurality of transmissionbeams (tx-beam #1). The transceiver receives a downlink control channelcandidate (PDCCH candidate) and a corresponding demodulation referencesignal (DM-RS) from the base station using one of a plurality ofreception beams (rx-beam #1) corresponding to the assumed one of theplurality of transmission beams (tx-beam #1). The processing circuitry(130) performs radio channel estimation based on the receiveddemodulation reference signal (DM-RS). The processing circuitry,depending on a radio channel estimation quality, demodulates thedownlink control channel candidate (PDCCH candidate) using the radiochannel estimation. The channel estimation is performed using ademodulation reference signal sequence which is generated observing anassociation which is associating the generated sequence with the assumedone of the plurality of transmission beams (tx-beam #1) such that atleast two of the plurality of transmission beams are associated withdifferent demodulation reference signal sequences.

According to a second aspect provided in addition to the first aspect,wherein performing the radio channel estimation includes:

-   -   the processing circuitry (130), in operation, correlating the        received demodulation reference signal (DM-RS) with the        generated demodulation reference signal sequence, and    -   the processing circuitry (130), in operation, determining a        radio channel estimation quality based on the correlation        result,

In addition or alternatively, in case the radio channel estimationquality is below a threshold, the processing circuitry (130) does notdemodulate the received downlink control channel candidate.

According to a third aspect provided in addition to the first or secondaspect, the processing circuitry (130) generates the demodulationreference signal sequence from a base sequence (modified scrambling-ID)which includes:

-   -   an identification of the assumed one of the plurality of        transmission beams (tx-beam ID),    -   such that the generated demodulation reference signal sequence        is associated with the assumed one of the plurality of        transmission beams (tx-beam #1).

According to a fourth aspect provided in addition to the third aspect,the processing circuitry (130) generates the demodulation referencesignal sequence from the base sequence (modified scrambling-ID) whichadditionally includes at least one of:

-   -   at least a part of an identification of the cell (Cell-ID)        comprising the assumed transmission beam, and    -   at least a part of an identification of the network (PLMN-ID)        comprising the cell,

The at least parts of the identification of the cell or of the networkcorrespond to a predetermined number of least significant bits of therespective identification.

According to a fifth aspect provided in addition to the third or fourthaspect, the processing circuitry (130) de-scrambles the demodulateddownlink control channel candidate using the base sequence.

According to a sixth aspect provided in addition to any of the first,second and fifth aspects, the processing circuitry (130) generates thedemodulation reference signal sequence from a base sequencecorresponding to a scrambling identification (scrambling-ID) includingusing an orthogonal cover code which is associated with the assumed oneof the plurality of transmission beams (tx-beam #1).

According to a seventh aspect provided in addition to any of the first,second and fifth aspects, the processing circuitry (130) generates thedemodulation reference signal sequence from a base sequencecorresponding to a scrambling identification (scrambling-ID) includingapplying a cyclic shift to the demodulation reference signal sequencecorresponding to a cyclic shift value which is associated with theassumed one of the plurality of transmission beams (tx-beam #1).

According to an eighth aspect provided in addition to any of the firstto seventh aspects, the demodulated downlink control channel candidateis included in a common search space carrying downlink controlinformation (DCI) which is intended for a group of plural mobileterminals. The downlink control information (DCI) corresponds to atleast DCI-Format 1-0 with a CRC scrambled with a random access radionetwork temporary identifier (RA-RNTI).

According to a ninth aspect provided in addition to any of the first toeighth aspects, the demodulated downlink control channel candidate isincluded in a common search space carrying downlink control information(DCI) which is intended for a group of plural mobile terminals. Thedownlink control information (DCI) corresponds to at least one of aDCI-Format 2_0 or any other DCI-format conveying indications of achannel occupation time (COT) structure with a CRC scrambled with a slotformat radio network temporary identifier (SFI-RNTI).

According to a tenth aspect provided in addition to any of the first toninth aspects, in case the transceiver (120) receives a configuration ofmonitoring locations for channel occupation time (COT) indications, theprocessing circuitry (130), in operation and at the monitoringlocations:

-   -   performs the channel estimation using the demodulation reference        signal sequence which is associated with the assumed one of the        plurality of transmission beams (tx-beam #1), and,    -   additionally performs, in case the radio channel estimation        quality is below a threshold, the channel estimation using a        different demodulation reference signal sequence which is        associated with another one of the plurality of transmission        beams (tx-beam #2).

In case the radio channel estimation quality using the differentdemodulation reference signal sequence is above the threshold,

the processing circuitry (130) demodulates the received downlink controlchannel (PDCCH) candidate and decodes the demodulated downlink controlchannel (PDCCH) candidate carrying downlink control information (DCI)conveying an indication of a channel occupation time (COT) structure,and

the processing circuitry (130) configures the transceiver (120) to skipreceiving any downlink control channel candidates (PDCCH candidate) andcorresponding demodulation reference signals (DM-RS) from the basestation for the remaining channel occupation time (COT) durationincluded in the channel occupation time (COT) structure.

According to an eleventh aspect provided in addition to the tenthaspect, the transceiver (120) receives a configuration of monitoringlocations for the channel occupation time (COT) indications including abeam common preamble sequence at configured monitoring locations.

According to a twelfth aspect provided in addition to any one of thefirst to eleventh aspects, the processing circuitry (130) is providedwith information specifying that the base station is configured to usespecific time instances for a specific format of downlink controlchannel (PDCCH) and corresponding demodulation reference signal (DM-RS)transmissions to the mobile terminal with a specific wide transmissionbeam (tx-beam #0) which is different from the plurality of transmissionbeams. The transceiver (120) receives at a specific time instant adownlink control channel candidate (PDCCH candidate) of the specificformat and a corresponding demodulation reference signal (DM-RS) fromthe base station using one of the plurality of reception beams (rx-beam#0) suitable for receiving the specific wide transmission beam (tx-beam#0). The processing circuitry (130) performs radio channel estimationbased on the received demodulation reference signal (DM-RS) and,depending on a radio channel estimation quality, demodulates thedownlink control channel candidate (PDCCH candidate) using the radiochannel estimation, and decodes the demodulated downlink control channelcandidate according to the specific format. The specific formatprescribes the decoded downlink control channel candidate to carrydownlink control information including:

-   -   a time duration for which the downlink control information is        held to be valid, and    -   an identification of at least one of the plurality of        transmission beams (tx-beam #1) which is being used by the base        station for downlink control channel candidate (PDCCH candidate)        and a corresponding demodulation reference signal (DM-RS)        transmissions during at least a part of the time duration

The processing circuitry (130) uses the identification of at least oneof the plurality of transmission beams (tx-beam #1) to generatedemodulation reference signal sequences in relation to the associationwhich are to be used for performing channel estimation during the atleast a part of the time duration.

According to a thirteenth aspect, a base station is provided, comprisingprocessing circuitry and a transceiver. The processing circuitry (180)assumes that the mobile terminal is configured to use for downlinkcontrol channel (PDCCH) and corresponding demodulation reference signal(DM-RS) receptions at the mobile terminal one of a plurality ofreception beams (tx-beam #1). The transceiver (170) transmits a downlinkcontrol channel (PDCCH) and corresponding demodulation reference signal(DM-RS) to the mobile terminal using one of a plurality of transmissionbeams (tx-beam #1) corresponding to the assumed one of the plurality ofreception beams (tx-beam #1). The processing circuitry (180) modulatesthe downlink control channel (PDCCH) to be transmitted and generates ademodulation reference signal sequence to be transmitted as thecorresponding demodulation reference signal (DMRS). The demodulationreference signal sequence is generated observing an association which isassociating the generated sequence with the one of the plurality oftransmission beams (tx-beam #1) such that at least two of the pluralityof transmission beams are associated with different demodulationreference signal sequences.

According to a fourteenth aspect, a reception method for a mobileterminal is provided. The mobile terminal assumes that a base station isconfigured to use for downlink control channel (PDCCH) and correspondingdemodulation reference signal (DM-RS) transmissions to the mobileterminal one of a plurality of transmission beams (tx-beam #1). Themobile terminal receives a downlink control channel candidate (PDCCHcandidate) and a corresponding demodulation reference signal (DM-RS)from the base station using one of a plurality of reception beams(rx-beam #1) corresponding to the assumed one of the plurality oftransmission beams (tx-beam #1). The mobile terminal performs radiochannel estimation based on the received demodulation reference signal(DM-RS) and, depending on a radio channel estimation quality,demodulates the downlink control channel candidate (PDCCH candidate)using the radio channel estimation. The channel estimation is performedusing a demodulation reference signal sequence which is generatedobserving an association which is associating the generated sequencewith the assumed one of the plurality of transmission beams (tx-beam #1)such that at least two of the plurality of transmission beams areassociated with different demodulation reference signal sequences.

According to a fifteenth aspect, a transmission method for a basestation is provided. The base station assumes that the mobile terminalis configured to use for downlink control channel (PDCCH) andcorresponding demodulation reference signal (DM-RS) receptions at themobile terminal one of a plurality of reception beams (tx-beam #1). Thebase station transmits a downlink control channel (PDCCH) andcorresponding demodulation reference signal (DM-RS) to the mobileterminal using one of a plurality of transmission beams (tx-beam #1)corresponding to the assumed one of the plurality of reception beams(tx-beam #1). The base station modulates the downlink control channel(PDCCH) to be transmitted and generates a demodulation reference signalsequence to be transmitted as the corresponding demodulation referencesignal (DMRS). The demodulation reference signal sequence is generatedobserving an association which is associating the generated sequencewith the one of the plurality of transmission beams (tx-beam #1) suchthat at least two of the plurality of transmission beams are associatedwith different demodulation reference signal sequences.

Hardware and Software Implementation of the Present Disclosure

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in the each embodiment may be controlled partly or entirely bythe same LSI or a combination of LSIs.

The LSI may be individually formed as chips, or one chip may be formedso as to include a part or all of the functional blocks. The LSI mayinclude a data input and output coupled thereto. The LSI here may bereferred to as an IC (integrated circuit), a system LSI, a super LSI, oran ultra LSI depending on a difference in the degree of integration.However, the technique of implementing an integrated circuit is notlimited to the LSI and may be realized by using a dedicated circuit, ageneral-purpose processor, or a special-purpose processor. In addition,a FPGA (Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuit cells disposed inside the LSIcan be reconfigured may be used.

The present disclosure can be realized as digital processing or analogueprocessing. If future integrated circuit technology replaces LSIs as aresult of the advancement of semiconductor technology or otherderivative technology, the functional blocks could be integrated usingthe future integrated circuit technology. Biotechnology can also beapplied.

The present disclosure can be realized by any kind of apparatus, deviceor system having a function of communication, which is referred as acommunication apparatus.

Some non-limiting examples of such communication apparatus include aphone (e.g., cellular (cell) phone, smart phone), a tablet, a personalcomputer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digitalstill/video camera), a digital player (digital audio/video player), awearable device (e.g., wearable camera, smart watch, tracking device), agame console, a digital book reader, a telehealth/telemedicine (remotehealth and medicine) device, and a vehicle providing communicationfunctionality (e.g., automotive, airplane, ship), and variouscombinations thereof.

The communication apparatus is not limited to be portable or movable,and may also include any kind of apparatus, device or system beingnon-portable or stationary, such as a smart home device (e.g., anappliance, lighting, smart meter, control panel), a vending machine, andany other “things” in a network of an “Internet of Things (IoT).”

The communication may include exchanging data through, for example, acellular system, a wireless LAN system, a satellite system, etc., andvarious combinations thereof.

The communication apparatus may comprise a device such as a controlleror a sensor, which is coupled to a communication device performing afunction of communication described in the present disclosure. Forexample, the communication apparatus may comprise a controller or asensor that generates control signals or data signals, which are used bya communication device performing a communication function of thecommunication apparatus.

The communication apparatus also may include an infrastructure facility,such as a base station, an access point, and any other apparatus, deviceor system that communicates with or controls apparatuses such as thosein the above non-limiting examples.

Further, the various embodiments may also be implemented by means ofsoftware modules, which are executed by a processor or directly inhardware. Also a combination of software modules and a hardwareimplementation may be possible. The software modules may be stored onany kind of computer readable storage media, for example RAM, EPROM,EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. It shouldbe further noted that the individual features of the differentembodiments may individually or in arbitrary combination be subjectmatter to another embodiment.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments. The present embodiments are,therefore, to be considered in all respects to be illustrative and notrestrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A mobile terminal comprising: a processingcircuitry which, in operation, assumes that a base station is configuredto use for downlink control channel and corresponding demodulationreference signal transmissions to the mobile terminal one of a pluralityof transmission beams; and a transceiver which, in operation, receives adownlink control channel candidate and a corresponding demodulationreference signal from the base station using one of a plurality ofreception beams corresponding to the assumed one of the plurality oftransmission beams; wherein, the processing circuitry, in operation,performs radio channel estimation based on the received demodulationreference signal and, depending on a radio channel estimation quality,demodulates the downlink control channel candidate using the radiochannel estimation, wherein, the channel estimation is performed using ademodulation reference signal sequence which is generated observing anassociation which is associating the generated sequence with the assumedone of the plurality of transmission beams such that at least two of theplurality of transmission beams are associated with differentdemodulation reference signal sequences, wherein, in case thetransceiver receives a configuration of monitoring locations for channeloccupation time indications, the processing circuitry, in operation andat the monitoring locations: performs the channel estimation using thedemodulation reference signal sequence which is associated with theassumed one of the plurality of transmission beams; and additionallyperforms, in case the radio channel estimation quality is below athreshold, the channel estimation using a different demodulationreference signal sequence which is associated with another one of theplurality of transmission beams, wherein, in case the radio channelestimation quality using the different demodulation reference signalsequence is above the threshold, the processing circuitry, in operation,demodulates the received downlink control channel candidate and decodesthe demodulated downlink control channel candidate carrying downlinkcontrol information conveying an indication of a channel occupation timestructure; and the processing circuitry, in operation, configures thetransceiver to skip receiving any downlink control channel candidatesand corresponding demodulation reference signals from the base stationfor the remaining channel occupation time duration included in thechannel occupation time structure.
 2. The mobile terminal according toclaim 1, wherein performing the radio channel estimation includes: theprocessing circuitry correlating the received demodulation referencesignal with the generated demodulation reference signal sequence; andthe processing circuitry determining a radio channel estimation qualitybased on the correlation result, and/or wherein, in case the radiochannel estimation quality is below a threshold, the processingcircuitry does not demodulate the received downlink control channelcandidate.
 3. The mobile terminal according to claim 1, wherein theprocessing circuitry, in operation, generates the demodulation referencesignal sequence from a base sequence which includes: an identificationof the assumed one of the plurality of transmission beams, such that thegenerated demodulation reference signal sequence is associated with theassumed one of the plurality of transmission beams.
 4. The mobileterminal according to claim 3, wherein the processing circuitry, inoperation, generates the demodulation reference signal sequence from thebase sequence which additionally includes at least one of: at least apart of an identification of the cell comprising the assumedtransmission beam; and at least a part of an identification of thenetwork comprising the cell; wherein, the at least parts of theidentification of the cell or of the network correspond to apredetermined number of least significant bits of the respectiveidentification.
 5. The mobile terminal according to claim 3, wherein theprocessing circuitry, in operation, de-scrambles the demodulateddownlink control channel candidate using the base sequence.
 6. Themobile terminal according to claim 1, wherein the processing circuitry,in operation, generates the demodulation reference signal sequence froma base sequence corresponding to a scrambling identification includingusing an orthogonal cover code which is associated with the assumed oneof the plurality of transmission beams.
 7. The mobile terminal accordingto claim 1, wherein the processing circuitry, in operation, generatesthe demodulation reference signal sequence from a base sequencecorresponding to a scrambling identification including applying a cyclicshift to the demodulation reference signal sequence corresponding to acyclic shift value which is associated with the assumed one of theplurality of transmission beams.
 8. The mobile terminal according toclaim 1, wherein the demodulated downlink control channel candidate isincluded in a common search space carrying downlink control informationwhich is intended for a group of plural mobile terminals, and thedownlink control information corresponds to at least DCI-Format 1-0 witha CRC scrambled with a random access radio network temporary identifier.9. The mobile terminal according to claim 1, wherein the demodulateddownlink control channel candidate is included in a common search spacecarrying downlink control information which is intended for a group ofplural mobile terminals, and the downlink control informationcorresponds to at least one of a DCI-Format 2_0 or any other DCI-formatconveying indications of a channel occupation time structure with a CRCscrambled with a slot format radio network temporary identifier.
 10. Themobile terminal according to claim 1, wherein, the transceiver, inoperation, receives the configuration of monitoring locations forchannel occupation time indications including a beam common preamblesequence at configured monitoring locations.
 11. The mobile terminalaccording to claim 1, wherein: the processing circuitry, in operation,is provided with information specifying that the base station isconfigured to use specific time instances for a specific format ofdownlink control channel and corresponding demodulation reference signaltransmissions to the mobile terminal with a specific wide transmissionbeam which is different from the plurality of transmission beams; thetransceiver, in operation, receives at a specific time instant adownlink control channel candidate of the specific format and acorresponding demodulation reference signal from the base station usingone of the plurality of reception beams suitable for receiving thespecific wide transmission beam; and the processing circuitry, inoperation, performs radio channel estimation based on the receiveddemodulation reference signal and, depending on a radio channelestimation quality, demodulates the downlink control channel candidateusing the radio channel estimation, and decodes the demodulated downlinkcontrol channel candidate according to the specific format, wherein thespecific format prescribes the decoded downlink control channelcandidate to carry downlink control information including: a timeduration for which the downlink control information is held to be valid;and an identification of at least one of the plurality of transmissionbeams which is being used by the base station for downlink controlchannel candidate and a corresponding demodulation reference signaltransmissions during at least a part of the time duration, wherein theprocessing circuitry uses the identification of at least one of theplurality of transmission beams to generate demodulation referencesignal sequences in relation to the association which are to be used forperforming channel estimation during the at least a part of the timeduration.
 12. A base station, comprising: a processing circuitry which,in operation, assumes that a mobile terminal is configured to use fordownlink control channel and corresponding demodulation reference signalreceptions at the mobile terminal one of a plurality of reception beams;and a transceiver which, in operation, transmits a downlink controlchannel and a corresponding demodulation reference signal to the mobileterminal using one of a plurality of transmission beams corresponding tothe assumed one of the plurality of reception beams; wherein, theprocessing circuitry, in operation, modulates the downlink controlchannel to be transmitted and generates a demodulation reference signalsequence to be transmitted as the corresponding demodulation referencesignal, wherein, the demodulation reference signal sequence is generatedobserving an association which is associating the generated sequencewith the one of the plurality of transmission beams such that at leasttwo of the plurality of transmission beams are associated with differentdemodulation reference signal sequences, wherein, the transceivertransmits a configuration of monitoring locations for channel occupationtime indications, wherein the monitoring locations are configured forthe mobile terminal to perform radio channel estimation using thedemodulation reference signal sequence which is associated with theassumed one of the plurality of transmission beams and additionallyusing a different demodulation reference signal sequence which isassociated with another one of the plurality of transmission beams, andwherein the downlink control channel carries downlink controlinformation conveying an indication of a channel occupation timestructure for use by the mobile terminal to skip receiving any downlinkcontrol channels and corresponding demodulation reference signals fromthe base station for the remaining channel occupation time durationincluded in the channel occupation time structure.
 13. A receptionmethod for a mobile terminal, comprising: assuming that a base stationis configured to use for downlink control channel and correspondingdemodulation reference signal transmissions to the mobile terminal oneof a plurality of transmission beams; receiving a downlink controlchannel candidate and a corresponding demodulation reference signal fromthe base station using one of a plurality of reception beamscorresponding to the assumed one of the plurality of transmission beams;performing radio channel estimation based on the received demodulationreference signal and, depending on a radio channel estimation quality,demodulating the downlink control channel candidate using the radiochannel estimation, wherein, the channel estimation is performed using ademodulation reference signal sequence which is generated observing anassociation which is associating the generated sequence with the assumedone of the plurality of transmission beams such that at least two of theplurality of transmission beams are associated with differentdemodulation reference signal sequences; receiving a configuration ofmonitoring locations for channel occupation time indications;performing, at the monitoring locations, the channel estimation usingthe demodulation reference signal sequence which is associated with theassumed one of the plurality of transmission beams; additionallyperforming at the monitoring locations, in case the radio channelestimation quality is below a threshold, the channel estimation using adifferent demodulation reference signal sequence which is associatedwith another one of the plurality of transmission beams; in case theradio channel estimation quality using the different demodulationreference signal sequence is above the threshold, demodulating thereceived downlink control channel candidate and decoding the demodulateddownlink control channel candidate carrying downlink control informationconveying an indication of a channel occupation time structure; andconfiguring to skip receiving any downlink control channel candidatesand corresponding demodulation reference signals from the base stationfor the remaining channel occupation time duration included in thechannel occupation time structure.
 14. A transmission method for a basestation, comprising assuming that a mobile terminal is configured to usefor downlink control channel and corresponding demodulation referencesignal receptions at the mobile terminal one of a plurality of receptionbeams; transmitting a downlink control channel and a correspondingdemodulation reference signal to the mobile terminal using one of aplurality of transmission beams corresponding to the assumed one of theplurality of reception beams; modulating the downlink control channel tobe transmitted and generating a demodulation reference signal sequenceto be transmitted as the corresponding demodulation reference signal,wherein, the demodulation reference signal sequence is generatedobserving an association which is associating the generated sequencewith the one of the plurality of transmission beams such that at leasttwo of the plurality of transmission beams are associated with differentdemodulation reference signal sequences, transmitting a configuration ofmonitoring locations for channel occupation time indications, whereinthe monitoring locations are configured for the mobile terminal toperform radio channel estimation using the demodulation reference signalsequence which is associated with the assumed one of the plurality oftransmission beams and additionally using a different demodulationreference signal sequence which is associated with another one of theplurality of transmission beams, and wherein the downlink controlchannel carries downlink control information conveying an indication ofa channel occupation time structure for use by the mobile terminal toskip receiving any downlink control channels and correspondingdemodulation reference signals from the base station for the remainingchannel occupation time duration included in the channel occupation timestructure.